An active analogue surround sound system that is the standard on VHS tape and most current television broadcasts. A Dolby Prologic decoder takes in two-channel, Dolby Surround-encoded audio and converts it into left, right, center, and surround channels.
True 'Cinema Style' surround sound from 5 speakers (2 x front, 2 x rear, 1 centre).
This is the English and pan-European name for Dolby Surround, an analogue format for surround sound where there is no digital connection necessary, just normal stereo (phono) outputs/inputs. The amplifier on the receiving end must be capable of Dolby Pro Logic decoding. The main difference between this and Dolby Digital is that the rear speakers are in mono (both output exactly the same) and there is no dedicated subwoofer channel. Of surround sound televisions actually sold the majority are of Pro-Logic standard though most offer little hope of upgrade ability.
More advanced form of Dolby Surround that not only recovers the surround information from the encoded program material, but also adds a center channel to keep dialogue and center effects firmly positioned on the TV screen. Provides a wider listening/viewing area and provides better channel separation. http://www.dolby.com/tech/#head2
This is the surround sound format from Dolby Labs before dolby digital. It is still found in many places and analog sources such as VHS tapes still carry it as the highest available surround sound format. Prologic is produced by taking the two channel source audio track and extracting the center and surround information from it. While the surround sound effect is adequate it is far less effective and spectacular than Dolby Digital. All Dolby Digital receivers are capable of playing back Prologic tracks but older prologic receivers cannot play Dolby Digital. However if your Prologic receiver has a 5.1 input then an external Dolby Digital decoder (such as an on board DVD player decoder) can decode the DD 5.1 signal and pass it through the inputs, allowing the Prologic receiver to play full Dolby digital. see Dolby Labs
Is a four-channel system consisting of left, center, right and rear channel, (the single rear channel is usually played through two speakers).
An active matrix decoder that extracts four signals from 2 channel Dolby Surround encoded material. The four channels are left, center, and right front channels, and a single bandwidth limited mono surround channel. The amplitude-phase matrix decoder uses level difference between the two source channels, called LT and RT, to steer across left-center-right, and the phase difference to steer from front to surround.